According to the Motor Vehicle Safety Act of 1966, the NHTSA can open a recall investigation only when there's a safety-related defect that can cause death or injury—for example, those infamous Firestone tires—or when a vehicle does not meet the agency's standards. Despite the Tacoma's meager two-star rating, which means it has a 30 percent to 40 percent chance of rolling over should a crash occur, the car has not been found to have any specific defects. And there are currently no federal regulations that mandate a minimum rollover resistance score. (A Toyota spokesman told the New York Times that safety improvements were forthcoming in the 2004 model.)

But the mounting number of rollover-related deaths—over 10,000 a year, compared to just 4,000 in 1989—has spurred some legislative action. Last month, the Senate Commerce Committee approved a bill that would require the NHTSA to issue rules that would alleviate the lethality of rollover accidents, most likely by toughening requirements on roof strength.

The bill follows the TREAD Act of 2000, which requires the NHTSA to come up with "real-world" rollover tests. The current rating system relies exclusively on a mathematical formula that factors together a vehicle's width, height, and center of gravity to determine the likelihood of rollover. Later this year, though, the agency will begin conducting tests with crash-test dummies in which the vehicles will be programmed to make indelicate maneuvers known as "j-turns" and "fishhooks." The tests are designed to give the NHTSA a better sense of how to prevent rollover and how to protect those unfortunate drivers who find themselves upside-down.

Bonus Explainer: The majority of recalls are voluntary, rather than compelled by the NHTSA. In 2001, for example, of the 14.5 million vehicles that went back to the manufacturer, an estimated 11 million were recalled voluntarily.